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La evidencia para el túnel nuclear mediado por radicales de proteínas en ácidos grasos alfa-oxigenasa
Ankur Gupta1, Arnab Mukherjee, Kenji Matsui
1Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore Maryland 21218, USA.
Journal of the American Chemical Society
|August 6, 2008
Resumen
La alfa-oxigenasa de arroz (RalphaO) utiliza un radical tirosílico para la oxidación de ácidos grasos, lo que ha sido confirmado por estudios de mutantes y efectos de grandes isótopos de deuterio. Esta enzima muestra un túnel cuántico significativo en su mecanismo radical.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Enzimología Enzimología.
- Biología Cuántica Biología cuántica.
Sus antecedentes:
- La alfa-oxigenasa del arroz (RalphaO) cataliza la inserción de O2 en los enlaces Calpha-H de los ácidos grasos.
- Se supone que su mecanismo involucra un radical tirosilo, similar a las ciclooxigenasas.
Objetivo del estudio:
- Para investigar el mecanismo catalítico de la alfa-oxigenasa de arroz (RalphaO).
- Para confirmar la participación de un radical tirosilo catalítico en la función RalphaO.
- Para explorar los efectos cuánticos en la catálisis enzimática.
Principales métodos:
- Mutagénesis dirigida al sitio (mutante Tyr379Phe).
- Estudios cinéticos. estudios de la cinética.
- Análisis espectroscópico.
- Mediciones del efecto del isótopo cinético del deuterio.
Principales resultados:
- La evidencia apoya un mecanismo irreversible de abstracción del átomo de hidrógeno.
- Se confirmó el papel catalítico del radical tirosilo (Tyr*).
- Se observaron efectos de isótopos cinéticos de deuterio muy grandes e independientes de la temperatura (~ 50).
Conclusiones:
- La alfa-oxigenasa de arroz (RalphaO) emplea un radical tirosílico para la catálisis.
- El túnel nuclear extenso contribuye significativamente al mecanismo de reacción de la enzima.
- RalphaO representa una nueva instancia de efectos cuánticos en las enzimas radicales de aminoácidos.
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